Does a Predictive Minimal Model of Friction-Induced Vibration Exist?

Highly idealised models of friction-induced vibration have been motivated by an attempt to capture what is essential to the phenomenon. This approach has resulted in a few simple mechanisms that are thought to capture common routes to instability. This paper aims to determine how well these perform as approximations to a more complex system, and whether the essential ingredients needed for a minimal model can be identified. We take a reduced-order model that exemplifies ‘mode-coupling’ and explore the extent to which it can approximate predictions based on an experimentally identified test-system. For the particular test system under study, two-mode ‘mode-coupling’ is rarely a good approximation and three modes are usually required to model a limited frequency range. We then compare predictions with results from an extensive program of sliding contact tests on a pin-on-disc rig in order to identify which ingredients are needed to explain observed squeal events. The results suggest that several minimal models would be needed to describe all observed squeal initiations, but the ‘negative-damping’ route to instability, which requires a velocity-dependent friction law, convincingly accounts for one cluster.